Just saw this message. Yes, in Runaways they mention a CTCs, and in real life the only way CTCs work is when you use the Deutsch proposition (which is branching off, and is mentioned in Endgame.) Also, according to "The Art of Avengers: Endgame", the design of the Quantum Realm Time Machine is based off how a CTC would look like in real life.^ I'm kinda open to this idea of the White Monolith tapping into the Quantum Realm for it's time travel use. (Especially since they were manmade by an alien.)
I guess...Gibborim's do have more knowledge and a different method of time travel that affects time and reality like you're suggesting A13G10..
EDIT: Ah okay, I see in the Runaways finale they did mention the "closed timelike curve" as the method they used. I guess that makes it different than the Monolith and Quantum Realm methods.
The Gibborim's method CANNOT rewrite a timeline. Marvel Television does not introduce something we haven't seen in the films. In the films, you cannot rewrite (yet), therefore the Runaways show is not rewriting. A friend asked Quinton Pebbles (a crew member of Runaways) and he said the time travel method is an open book because they did not write rules for it.
We have to take the CTCs method helps you to create a branched timeline, but when you do, if your version cannot be in that timeline, you are either taken out or are erased.